I'm thinking to move to Oly OMD EM5 with a Nauticam housing, and one thing I would like to use is a external straight viewfinder (Inon or Nauticam). I'm been suffering on internet, trying to find any photo of how the VF fit on the housing, and if the LCD screen is covered or not by the VF-

If somebody is using this rig, could be useful if give me their comments and could be great if paste a photo of this rig

http://www.flickr.co...in/photostream/
You need to order a special back window for viewfinder that can accommodate either Inon or Nauticam viewfinder.
I am using the Nauticam 45 viewfinder, which is very nice !!

here is a link to a picture of the special back window that Edmond mentioned (I have no connections with this company). At the Photokina here in Germany Mr. Lai from Nauticam demonstrated that this window is easily exchangeable by the user.

As you can see, with this window a certain part of the LCD is blocked when no external viewfinder is mounted.

Just to clarify this part of your question, yes, with the LCD window changeout (which is pretty easily done and requires no tools) you can then use our 180º VF. You could use the Inon as well, but it would require an adapter or conversion to the Nauticam format.

I purchased this same set-up from Reef, using the 45 degree finder. First off, I HIGHLY recommend it. The standard Nauty finder is OK and useable, but the external finder is like going to the moview by comparison.

It does cover the LCD screen a little, but, once you use it, you will not be using the screen. I have done two dives and shot 200 images and videos, and not once have I felt the need to look at the LCD screen. Remember that the EVF can show you all the settings so even if you have to go change a setting in a menu there is no need to use the screen. I believe that, because of the more compact dimensions of the EM5 housing (ie the viewfinder is close to the ldc screen) that even the straight finder will also block the screen somewhat.

You might want to consider the 45 degree unless you already have the straight finder. The EM5 housing is very compact, such that using the 45 degree finder is no effort at all as you are not moving a huge bulky housing underneath you. It's hard to describe but very evident in use. I have no issue using the 45 for wide angle shots. For macro, it is far superior to the streaight finder as you can have the camera below you and stay off the bottom.